U.S. patent number 11,000,162 [Application Number 16/071,595] was granted by the patent office on 2021-05-11 for multi-ply fibrous product comprising a laminating adhesive with a dermatologically acceptable acid.
This patent grant is currently assigned to Essity Hygiene and Health Aktiebolag. The grantee listed for this patent is ESSITY HYGIENE AND HEALTH AKTIEBOLAG. Invention is credited to Alain Bohn, Yves Enggasser, Daniel Hagberg, Emilie Pleyber, Frederic Roesch, Pascale Saas, Clive Smith.
United States Patent |
11,000,162 |
Saas , et al. |
May 11, 2021 |
Multi-ply fibrous product comprising a laminating adhesive with a
dermatologically acceptable acid
Abstract
A multi-ply fibrous product includes at least two fibrous plies,
such as a multi-ply nonwoven product, a tissue paper product or a
hybrid thereof including at least two tissue paper plies and/or
nonwoven plies including cellulosic fibers. At least two fibrous
plies are bonded to each other by an aqueous adhesive composition
including an adhesive component and a dermatologically acceptable
acid, and optionally a salt thereof. A process for the manufacture
of this multi-ply fibrous product includes (a) providing at least
two fibrous webs, (c) applying an aqueous adhesive composition
including an adhesive component and a water-soluble,
dermatologically acceptable acid, and optionally the corresponding
salt thereof, to at least one side of at least one fibrous web, d)
superimposing at least two webs such that the aqueous adhesive
composition is located between at least two superimposed webs, and
e) bonding at least two webs together.
Inventors: |
Saas; Pascale (Kirchheim,
DE), Pleyber; Emilie (Selestat, FR),
Hagberg; Daniel (Gothenburg, SE), Bohn; Alain
(Kunheim, FR), Roesch; Frederic (Colmar,
FR), Enggasser; Yves (Biesheim, FR), Smith;
Clive (Brussels, BE) |
Applicant: |
Name |
City |
State |
Country |
Type |
ESSITY HYGIENE AND HEALTH AKTIEBOLAG |
Gothenburg |
N/A |
SE |
|
|
Assignee: |
Essity Hygiene and Health
Aktiebolag (Gothenburg, SE)
|
Family
ID: |
1000005543785 |
Appl.
No.: |
16/071,595 |
Filed: |
January 27, 2016 |
PCT
Filed: |
January 27, 2016 |
PCT No.: |
PCT/EP2016/051716 |
371(c)(1),(2),(4) Date: |
July 20, 2018 |
PCT
Pub. No.: |
WO2017/129240 |
PCT
Pub. Date: |
August 03, 2017 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20190021553 A1 |
Jan 24, 2019 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D21H
27/32 (20130101); A47K 10/16 (20130101); D21H
27/30 (20130101); B31F 1/07 (20130101); D21H
27/002 (20130101); D21H 27/40 (20130101); D04H
1/593 (20130101); B31F 2201/0764 (20130101); B31F
2201/0733 (20130101); B31F 2201/0787 (20130101); B31F
2201/0738 (20130101) |
Current International
Class: |
A47K
10/16 (20060101); B31F 1/07 (20060101); D21H
27/30 (20060101); D21H 27/00 (20060101); D21H
27/32 (20060101); D21H 27/40 (20060101); D04H
1/593 (20120101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1468115 |
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Jan 2004 |
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CN |
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0991436 |
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Apr 2000 |
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EP |
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2248809 |
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Mar 2005 |
|
RU |
|
2435668 |
|
Dec 2011 |
|
RU |
|
201110692 |
|
Aug 2012 |
|
RU |
|
WO-98/57677 |
|
Dec 1998 |
|
WO |
|
WO-01/29315 |
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Apr 2001 |
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WO |
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WO-0228447 |
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Apr 2002 |
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WO |
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WO-2006/068751 |
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Jun 2006 |
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WO |
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WO-2006068751 |
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Jun 2006 |
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WO |
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WO-2007/108725 |
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Sep 2007 |
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WO |
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WO-2008/131071 |
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Oct 2008 |
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WO |
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WO-2017129240 |
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Aug 2017 |
|
WO |
|
Other References
Colombian Office Action Oficio N.degree. 1054 dated Jan. 22, 2020
issued in Colombian patent application No. NC2018/0007637 (12
pages) and its partial English-language translation therof (7
pages). cited by applicant .
Decision to Grant, along with its English-language tranlation, that
issued in Russian patent application No. 2018130595/05 (049751)
dated Aug. 9, 2019 attached. cited by applicant .
English-language translation of Official Action and Search Report
that issued in Russian patent application No. 2018130595/05
(049751) dated Apr. 24, 2019 attached. cited by applicant .
Colombian Office Action Oficio N.degree. 5695 dated May 20, 2020
issued in Colombian patent application No. NC2018/0007637 (12
pages) and its partial English-language translation thereof (5
pages). cited by applicant .
Chinese Patent Office, Second Office Action issued in CN
Application No. 201680080339A, dated Jan. 22, 2021 (with English
language translation), 13 pages. cited by applicant.
|
Primary Examiner: Fortuna; Jose A
Attorney, Agent or Firm: Wood Herron & Evans LLP
Claims
The invention claimed is:
1. A multi-ply fibrous product comprising at least two fibrous
plies selected from the group consisting of: (a) a multi-ply
nonwoven product comprising at least two nonwoven plies comprising
cellulosic fibres, (b) a tissue paper product comprising at least
two tissue paper plies, and (c) a hybrid thereof comprising at
least one tissue paper ply and at least one nonwoven ply comprising
cellulosic fibers, wherein said at least two plies are bonded to
each other by an aqueous adhesive composition comprising an
adhesive component and a dermatologically acceptable and water
soluble acid selected from the group consisting of inorganic acids;
hydroxylated, organic acids having 2 to 24 carbon atoms; polymeric
organic acids; and combinations thereof, wherein said acid and
optionally a salt thereof are provided in such an amount that the
pH of the multi-ply fibrous product measured according to ISO
6588-1:2012(E) is in the range of from 3.5 to 6.
2. The multi-ply fibrous product as set forth in claim 1, wherein
the aqueous adhesive composition contains the acid and optionally
the salt thereof in a molar amount of 0.1 to 10 mol/1.
3. The multi-ply fibrous product as set forth in claim 1, wherein
the aqueous adhesive composition is present in an amount, based on
the total weight of all ingredients except water, of 0.01 to 2
wt.-% with respect to the weight of the multi-ply fibrous
product.
4. The multi-ply fibrous product as set forth in claim 1, wherein
the adhesive component is selected from (a) natural polymers
selected from the group consisting of proteins and protein-based
compounds, gums and gum-like materials, polysaccharide-based
materials, and glues derived from animal products, and (b)
synthetic polymers selected from the group consisting of PEI
(polyethyleneimine), PAE (polyamidoamin-epichlorhydrine) and PVAm
(polyvinylamine), polyvinyl alcohol (PVA), polyvinyl acetate
(PVAC), vinyl acetate-ethylene (VAE), polyvinylpyrrolidone (PVP),
polyurethanes and styrene-butadiene, and water-soluble or
dispersible cellulose-based compounds, and any combination
thereof.
5. The multi-ply fibrous product as set forth in claim 1, wherein
the aqueous adhesive composition contains the optionally present
salt thereof and the salt thereof corresponds to the selected
acid.
6. The multi-ply fibrous product as set forth in claim 1, wherein
the aqueous adhesive composition comprises a dermatologically
acceptable acid and a salt thereof and both are present in amounts
providing together a pH buffering capacity.
7. The multi-ply fibrous product as set forth in claim 1, wherein
the plies comprise paper-making fibers selected from the group
consisting of (i) only non-recycled cellulosic fibers, (ii) only
recycled cellulosic fibers, and (iii) a mixture of non-recycled
cellulosic fibers and recycled cellulosic fibers in a weight ratio
of 99/1 to 1/99.
8. The multi-ply fibrous product as set forth in claim 1, wherein
the number of plies is 2 to 8.
9. The multi-ply fibrous product as set forth in claim 1, wherein
the adhesive composition is applied in at least one regular or
irregular pattern to at least a part of the surface of the fibrous
plies, wherein said regular or irregular pattern(s) cover(s) at
least the central area of the fibrous plies.
10. The multi-ply fibrous product as set forth in claim 1, wherein
the multi-ply fibrous product, has two outer plies, wherein at
least one outer ply is embossed, thereby forming protuberances
wherein the aqueous adhesive composition is applied to the distal
end of at least a part of the protuberances which are arranged such
as to bond together the two outer plies.
11. The multi-ply fibrous product as set forth in claim 1, wherein
said multi-ply fibrous product comprises at least three plies
including an embossed upper outer ply, an embossed lower outer ply,
and a central ply, each outer ply comprising patterns in relief
including at least in part discrete protuberances, and a central
ply, the distal areas of at least part of the protuberances of each
outer ply facing the central ply, and at least one of the upper
outer ply and lower outer ply having a pattern density of at least
10 protuberances/cm.sup.2, the lower outer ply comprising a first
pattern and a second pattern, the height of the first pattern being
less than the height of the second pattern, wherein the central ply
and the upper outer ply are joined in a nested mode, and by the
applied adhesive composition, to said lower outer ply at a level of
at least part of the tips of the second pattern of said lower outer
ply, wherein the height of the protuberances of the second pattern
is 50% to 200% greater than the height of the protuberances of the
first pattern.
12. The multi-ply fibrous product as set forth in claim 1, wherein
the percentage of the total surface of the multi-ply fibrous
product which is bonded by the adhesive composition is 1 to
20%.
13. The multi-ply fibrous product as set forth in claim 1, wherein
said multi-ply fibrous product is selected from the group
consisting of a wipe, a sanitary product, a paper handkerchief, a
household towel, a towel, a tissue for facial use, a
napkin/serviette, bed linen and a garment, wherein the multi-ply
fibrous product has 2 to 8 plies.
Description
CROSS-REFERENCE TO PRIOR APPLICATION
This application is a .sctn. 371 National Stage Application of PCT
International Application No. PCT/EP2016/051716 filed Jan. 27,
2016, which is incorporated herein in its entirety.
DESCRIPTION
The present disclosure relates to a multi-ply fibrous product,
especially a nonwoven product, tissue paper product or hybrid
thereof, capable of contributing to a healthy skin pH, in
particular to a multi-ply fibrous product wherein the individual
plies are bonded to each other by means of an adhesive including a
dermatologically acceptable acid, and optionally a salt
thereof.
BACKGROUND
Nonwoven- and tissue paper-based materials find extensive use in
modern society. Toilet paper, paper towels such as hand towels or
household (kitchen) towels, facial tissues, napkins and tissue
handkerchiefs are staple items of commerce. These products
typically contain cellulosic fibres (papermaking pulp fibers)
selected from hardwood types, softwood types and non-wood types
like bamboo or Miscanthus. These products can also contain a blend
of cellulosic and non-cellulosic fibres.
Among the most important physical properties of tissue paper
products are their strength, their softness, their absorbency,
primarily for aqueous systems, and their lint and dust resistance.
These physical properties are generally tuned for addressing common
consumer demand.
Tissue paper products typically come in contact with the human skin
when being used. For this reason, it has been considered in the art
to treat certain tissue paper products such as toilet paper or
handkerchiefs with lotions containing various types of skin-care
components but also frequently pH-regulating substances. However,
facial tissues, napkins or household (kitchen) towels are typically
provided without lotion and also in respect of toilet papers or
handkerchiefs there is currently a greater demand for lotion-free
grades.
In respect of lotion-free products the present inventors have noted
that there is a discrepancy between the pH of conventional tissue
paper products and the pH of healthy skin. Depending on the origin
of the papermaking fibres, the pH of raw tissue paper webs which
have not been further processed is either very close to the neutral
point (pH of about 6.5), if mainly virgin papermaking fibres have
been used, or slightly basic (pH of about 8.5) if a greater
proportion of recycled fibres is included. The current pH level of
tissue paper products is hence between 6.5 and 8.5 whereas the pH
of healthy skin lies in the range between 4.5 and 6.0. This
slightly acidic pH is caused by the acid mantle of the human skin.
The acid mantle of the human skin is a very fine, slightly acidic
film on the surface of the skin acting as a barrier to bacteria,
viruses and other potential contaminants that might penetrate the
skin. Accordingly, it is important to minimize the impact of
external factors on skin pH.
The present inventors noted that it cannot be excluded that,
especially during longer or repeated contact with the human skin,
conventional lotion-free tissue paper products have a negative
impact on the pH of healthy skin. The same applies to nonwoven
products including cellulosic fibers.
Accordingly it is desired to provide a multi-ply fibrous product,
in particular nonwoven product, tissue paper product or a hybrid
thereof, that reduces the likelihood that conventional multi-ply
fibrous products change the pH of healthy skin.
It is also desired to provide a multi-ply fibrous product, in
particular nonwoven product, tissue paper product or a hybrid
thereof, with particularly efficient means to prevent a negative
impact of the pH of conventional multi-ply fibrous products on skin
pH.
Moreover, it is also desired to provide such a multi-ply fibrous
product without adversely affecting other properties related to the
use thereof such as delamination strength and/or softness and/or
absorbency and/or further properties known in the art.
SUMMARY
In an aspect, a multi-ply fibrous product includes at least two
fibrous plies, for example a multi-ply nonwoven product, a tissue
paper product or a hybrid thereof, including at least two tissue
paper plies and/or nonwoven plies including cellulosic fibers,
wherein at least two fibrous plies are bonded to each other by
means of an aqueous adhesive composition including an adhesive
component and a dermatologically acceptable acid, and optionally a
salt thereof.
In another aspect, a process for the manufacture of a multi-ply
fibrous product, such as a tissue paper product, includes: a)
providing at least two fibrous webs of tissue paper and/or
nonwoven; b) optionally embossing at least one web in order to
provide at least one pattern of protuberances; c) applying an
aqueous adhesive composition including an adhesive component and,
in particular embodiments, a water-soluble, dermatologically
acceptable acid, and optionally the corresponding salt thereof, to
at least one side of at least one fibrous web, wherein, if at least
one web is embossed, the aqueous adhesive composition can be
applied to the distal ends of at least a part of the protuberances;
d) superimposing at least two webs such that the aqueous adhesive
composition is located between at least two superimposed webs; e)
bonding at least two webs together; and f) optionally further steps
for converting the bonded webs to the final multi-ply fibrous
product.
Particular embodiments of the multi-ply fibrous product and/or the
aqueous adhesive composition are described below and in the
claims.
In embodiments of the multi-ply fibrous product as set forth above,
said acid and optionally the salt thereof are provided in such an
amount that the pH of the multi-ply fibrous product measured
according to ISO 6588-1:2012(E) is in the range of from 3.5. to 7,
4 to 6.9, 4.3 to 6.4, or 4.5 to 6.2, e.g. 4.8 to 6.0. (It should be
noted that hereinafter the description of broader and narrower
ranges also discloses embodiments in which the lower and upper
limits are combined in a different manner. For example, the
following pH ranges: 3.5 to 6.9, 3.5 to 6.4, 3.5 to 6.2, 3.5 to
6.0, 4.0 to 7.0, 4.3 to 7.0, 4.5 to 7.0, 4.8 to 7.0, 4.0 to 6.4,
etc.)
In embodiments, the aqueous adhesive composition contains the acid,
and optionally the salt thereof, in a molar amount of 0.1 to 10
mol/1, 0.5 to 5 mol/l, or e.g. 1 to 3 mol/1.
In embodiments, the aqueous adhesive composition is present in an
amount, based on the total weight of all ingredients except water,
of 0.01 to 2 wt.-%, or 0.1 to 1.3 wt.-%, with respect to the weight
of the multi-ply fibrous product.
In embodiments, the adhesive component is selected from (a) natural
polymers such as proteins and protein-based compounds, gums and
gum-like materials, polysaccharide-based materials, glues derived
from animal products and (b) synthetic polymers such as PEI
(polyethyleneimine), PAE (polyamidoamin-epichlorhydrine) and PVAm
(polyvinylamine), polyvinyl alcohol (PVA), polyvinyl acetate
(PVAC), vinyl acetate-ethylene (VAE), polyvinylpyrrolidone (PVP),
polyurethanes and styrene-butadiene, and water-soluble or
dispersible cellulose-based compounds such as carboxymethyl
cellulose, sodium carboxymethyl cellulose, methyl cellulose, and
ethyl cellulose; or any combination thereof.
In embodiments, the dermatologically acceptable acid is water
soluble, and is selected from (i) inorganic acids such as boric
acid; (ii) optionally hydroxylated, organic acids having 2 to 24
carbon atoms, optionally hydroxylated, organic acids having 3 to 6
carbon atoms, or optionally citric acid, lactic acid, isoascorbic
acid, or combinations thereof; and (iii) polymeric organic acids
such as polyacrylic acid, and combinations thereof. In embodiments,
the optionally present salt thereof is the salt corresponding to
the selected acid.
In embodiments, the aqueous adhesive composition includes a
dermatologically acceptable acid and a salt thereof, and both are
present in amounts providing together a pH buffering capacity.
In embodiments, the plies include, as paper-making fibers, (i) only
non-recycled cellulosic fibers, (ii) only recycled cellulosic
fibers, or (iii) a mixture of non-recycled cellulosic fibers and
recycled cellulosic fibers in a weight ratio of 99/1 to 1/99, e.g.
90/10 to 10/90 or 80/20 to 20/80, wherein in any of (i), (ii) or
(iii) the cellulosic fibers can be selected from wood fibers such
as softwood or hardwood fibers and non-wood fibers such as fibers
from annual plants, and combinations thereof.
In embodiments, the number of plies, in particular tissue paper
plies, is 2 to 8, in particular 2 to 6, e.g. 2 to 5.
In embodiments, the adhesive composition is applied in at least one
regular or irregular pattern to at least a part of the surface of
the plies, in particular nonwoven or tissue paper plies, wherein
said regular or irregular pattern/s cover/s at least the central
area of the fibrous plies, in particular nonwoven or tissue paper
plies.
In embodiments, the multi-ply fibrous product is a tissue paper
product, has two outer plies, and optionally at least one further
ply located therebetween, wherein at least one outer ply is
embossed, thereby forming protuberances wherein the aqueous
adhesive composition is applied to the distal end of at least a
part of the protuberances which are arranged such, as to bond
together the two outer plies, and optionally at least one further
ply located therebetween.
In embodiments, the multi-ply fibrous product is a tissue paper
product, including at least three plies, an embossed upper outer
ply, and an embossed lower outer ply, each outer ply including
patterns in relief including at least in part discrete
protuberances, and a central ply, the distal areas of at least part
of the protuberances of each outer ply facing the central ply, and
at least one of the upper outer ply and lower outer ply having a
pattern density of at least 10, or at least 20
protuberances/cm.sup.2, the lower outer ply including a first
pattern and a second pattern, the height of the first pattern being
less than the height of the second pattern, wherein the central ply
and the upper outer ply are joined in a nested mode, and by means
of the applied adhesive composition, to said lower outer ply at a
level of at least part of the tips of the second pattern of said
lower outer ply, wherein the height of the protuberances of the
second pattern can be by 50% to 200% greater than the height of the
protuberances of the first pattern.
In embodiments, the percentage of the total surface of the
multi-ply fibrous product which is bonded by means of the adhesive
composition is 1 to 20%, 2 to 10%, or 4 to 8%.
In embodiments, the multi-ply fibrous product is selected from a
wipe, a sanitary product such as toilet paper, a paper
handkerchief, a household towel, a towel, a tissue for facial use,
a napkin/serviette, bed linen or a garment. In certain embodiments,
the multi-ply fibrous product is a toilet paper product having 2 to
8 plies, or 2 to 6 plies.
Hereinafter, the use of the terms "comprising" or "including"
should be understood as disclosing, as a more restricted
embodiment, the term "consisting of" as well, as long as this is
technically meaningful.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation illustrating an
embossing/gluing station which can be used for manufacturing a
three-ply tissue paper product. In FIG. 1, the following reference
numbers represent: (1) Ply A (1.sup.st outer ply), (2) Ply B
(middle ply), (3) Ply C (2.sup.nd outer ply), (4) Gluing unit, (5)
Gluing chamber, (6) Anilox roll (engraved), (7) Applicator roll
(flat rubber roller), (8a), (8b) Rubber rolls, (9a), (9b) Embossing
rolls, (10) Marrying roll, (11) Three-ply tissue paper product
The numbers, as in all figures, apply to all figures. The rotation
directions of the different rolls and the advancement direction of
the plies are indicated by the arrows.
FIG. 2 is a schematic representation illustrating the structure of
an embodiment of a three-ply tissue paper product. In FIG. 2, the
following reference numbers represent: (12) Glue (adhesive
composition), (13') Level 1 engraving (micro embossing), (14) Level
2 engraving (macro-embossing, decorative pattern).
FIGS. 3A and 3B are a schematic representation of the different
embossing patterns of the tissue paper product. In FIGS. 3A and 3B,
the following reference numbers represent: (15a, b) Micro-embossing
pattern, (16) Macro-embossing pattern.
FIG. 4 is a schematic representation of one part of the surface of
embossing roll (9a) shown in FIG. 1. The two different height
levels of engraved protrusions lead to corresponding different
embossment levels of the tissue paper product. In FIG. 4, the
following reference numbers represent: (13) Level 1 engraving, (14)
Level 2 engraving.
FIG. 5 is a schematic representation of an example of a
micro-embossing pattern of the tissue paper product. The dot number
is 20/cm.sup.2.
DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS
The present disclosure relates to a multi-ply fibrous product
including at least two fibrous plies. In particular embodiments,
the multi-ply-fibrous product is selected from:
(a) a multi-ply nonwoven product including at least two nonwoven
plies which plies, for example, include cellulosic fibres;
(b) a tissue paper product including at least two tissue paper
plies; and
(c) a hybrid thereof including at least one tissue paper ply and at
least one nonwoven ply, including, for example, cellulosic
fibers.
In this multi-ply fibrous product at least two of the
aforementioned fibrous plies are bonded to each other by means of
an aqueous adhesive composition including an adhesive component and
a dermatologically acceptable acid, and optionally a salt
thereof.
In a particular embodiment the multi-ply fibrous product is a
tissue paper product.
The tissue paper product, nonwoven product or hybrid thereof is
composed of two or more plies bonded to each other with a specific
adhesive composition.
The term "ply" as used herein refers to distinguishable and
typically separable cut-to-size webs of tissue paper as are
obtained after processing ("converting") one or more base (raw)
tissue paper webs. Each individual ply may include one or more
layers, e.g. one, two, three or four layers. In the case of
nonwovens, the term "ply" as used herein refers to distinguishable
and typically separable cut-to-size webs of nonwoven.
In connection with tissue paper webs the term "layer", as used
herein, refers to a stratum within the web having a defined fiber
composition. The one or more layers is/are formed by depositing one
or more streams of pulp furnishes onto a wire with a pressurized
single- or multi-layered headbox. This technique is well known to
those skilled in the art. It renders possible the use of different
kinds of fibers in each layer of the web.
As used herein, "tissue paper web" is understood to include the
one-ply base tissue as obtained from the tissue machine. The tissue
paper web is made by a process including the steps of: forming an
aqueous suspension of pulp fibers i.e. the so-called "furnish",
depositing said aqueous suspension onto a wire to form a wet web,
dewatering, drying and creping the web.
The tissue paper web and the resulting ply may have a basis weight
of 8 to 50 g/m.sup.2, in particular 10 to 30 g/m.sup.2, especially
12 to 25 g/m.sup.2. The same applies to nonwoven webs and the
resulting plies.
Based on the underlying compatibility of the production processes
(wet forming), "tissue" production is counted among the papermaking
techniques. The production of tissue is distinguished from paper
production by its extremely low basis weight and its much higher
tensile energy absorption index. Paper and tissue paper also differ
in general with regard to the modulus of elasticity that
characterizes the stress-strain properties of these planar products
as a material parameter.
A tissue's high tensile energy absorption index results from the
outer or inner creping. The former is produced by compression of
the paper web adhering to a dry cylinder as a result of the action
of a crepe doctor or in the latter instance as a result of a
difference in speed between two wires ("fabrics"). This causes the
still moist, plastically deformable paper web to be internally
broken up by compression and shearing, thereby rendering it more
stretchable under load than an uncreped paper. A high tensile
energy absorption index can also be achieved by imparting to the
tissue a 3D structure by means of the wires themselves. Most of the
functional properties typical of tissue and tissue products result
from the high tensile energy absorption index (see DIN EN 12625-4
and DIN EN 12625-5).
The tissue paper can be produced from paper-making fibers according
to "Conventional Processes" as in the manufacture of "Dry Crepe
Tissue" or "Wet Crepe Tissue" or "Processes for Structured Tissue"
such as the Through Air Drying (TAD) manufacturing method, the
manufacture of uncreped through-air dried (UCTAD) tissue, or
alternative manufacturing methods, e.g. the Advanced Tissue Molding
System (ATMOS) of the company Voith, or Energy Efficient
Technologically Advanced Drying eTAD of the company Georgia
Pacific, or Structured Tissue Technology SST of the company Metso
Paper. Hybrid processes like NTT (New textured Tissue) which are
alterations of the conventional processes can be used, too.
The conventional dry crepe manufacturing method includes: pressing
and drying the wet paper fibers as a sheet on a large-diameter,
heated cylinder (also called Yankee dryer); and subsequently
detaching and creping the sheet of dried paper fibers by means of a
metal blade applied against said cylinder, across its direction of
rotation. The creping operation creates undulations in the sheet
across its direction of travel. The creping operation increases the
thickness of the sheet, and confers elasticity and gives touch
(soft touch) properties to the sheet.
The TAD manufacturing method includes: molding the sheet of wet
paper fibers on a fabric; and subsequently drying the sheet, at
least partly, by means of a current of hot air passing through
it.
Subsequently, the dried sheet may be creped.
Further, in the manufacture of the tissue web to be used, a process
as described in PCT/EP2015/059326 (application date: 29 Apr. 2015;
title: "Tissue paper comprising pulp fibers originating from
Miscanthus and method for manufacturing the same", incorporated by
reference) can be used. Specifically reference is made to the
description and details of the TAD process (e.g. 3-D-shaped fabric,
permeable drying cylinder, etc.) disclosed therein. The parameters
described in this passage are also valid for the use of the ATMOS
technology.
Once, the tissue paper has been manufactured, a distinct
manufacturing operation called converting operation is typically
employed to form the tissue paper product (i.e. the paper towel,
toilet tissue rolls, bathroom tissue, wiping tissue, kitchen tissue
rolls, handkerchiefs, etc. . . . ).
The term "nonwoven" is very common in the art and can be further
defined in the manner described in ISO 9092:2011, for use herein.
Typical nonwoven manufacturing techniques include the air laid
technology, spun laid technology, dry laid technology, and wet laid
long fibers technology.
According to an embodiment, each of the nonwoven plies used in the
multi-ply fibrous product (i.e. multiply nonwoven product or the
nonwoven/tissue hybrid) includes cellulosic fibres. In this case,
the content of the cellulosic fibres, based on the total weight of
all fibres present in the respective ply, is at least 20 wt.-%, at
least 50 wt.-%, or at least 80 wt.-%. The remaining fibers are in
these cases non-cellulosic fibers such as synthetic fibers.
According to an embodiment, the fibrous multi-ply product includes
at least one, or at least 2 textured nonwoven plies. The
manufacture of textured nonwoven webs which can be used as nonwoven
ply/plies has been described for instance in WO2014/009784
(incorporated by reference). Referring to FIG. 12 of this
international application, a particular embodiment of the textured
nonwoven is produced as follows:
A reel of fluff pulp 30 is used as raw material. It is fed into
crusher 31. The fluff pulp is defibrized into fluff or free
papermaking fibers 32. Other raw material may be used, for example
blend of fluff pulp and synthetic fibers, artificial fibers or
other natural fibers (for instance cellulosic fibers), or
thermo-bonded fibers. The papermaking fibers 32 are fed into a
given number of (for example two) forming chambers 33. In the
forming chambers 33, the papermaking fibers 32 are transported by
means of an air flow. The papermaking fibers 32 are deposited onto
a forming fabric 34 that travels in loop below the forming chambers
33. Nearly before leaving the forming fabric 34, the formed web is
compacted by a compactor 35. The compacted web resulting from this
step is then transferred from the forming fabric 34 onto a transfer
fabric 36. A binder is sprayed onto one side of the compacted web
by a first binder sprayer 37. The binder is a latex composition
such as an ethylene and vinyl acetate copolymer composition. Then,
the compacted web is dried into a first drying unit 38 (e.g. at a
temperature of approximately 110-120.degree. C.). Subsequently, the
compacted web is calendered by means of a calendering section 39.
The calendering section 39 includes calendering rollers 40 and a
mating cylinder 41 in vis-a-vis, both rotating in opposite
directions. The calendering roller 40 can be a calendering roller
including a positive pattern. The mating cylinder 41 may be a
roller having a smooth surface (the mating cylinder may be made
from steel or rubber material). The calendering roller may be
heated. A calendered web 42 results from this step. A binder (e.g.
latex) is sprayed onto the other side of the calendered web 42 by a
second binder sprayer 43. As an alternative to the use of a binder
sprayed by the first and second binder sprayers 37, 43,
thermo-binding fibers (e.g. thermo-bonded fiber or thermo-bonded
fiber and latex) can be used and mixed with papermaking fibers into
the forming chambers 33. Then, the calendered web 42 is dried and
cured into a second drying unit 44 (e.g. at a temperature of
approximately 200.degree. C.). The resulting web 42 is further
cured and cooked by the means of a third drying unit 45 (e.g. at a
temperature of approximately 200.degree. C.). The calendered web
resulting from the above steps forms a textured nonwoven fabric
including papermaking fibers 46. It may be wound onto a reel 50 as
a roll of textured nonwoven fabric including papermaking fibers.
The reel 50 of textured nonwoven fabric including papermaking
fibers may then be fed into a converting unit 60 in order to
produce napkins, paper towels, toilet paper rolls, facial rolls,
wiping paper products, kitchen towel rolls, skin care or cleaning
wipes, handkerchiefs, etc. . . . .
The paper-making fibers (in the following also referred to as
"cellulosic fibers") can be produced from virgin and/or recycled
paper pulp raw material. The cellulosic fibres to be used may
contain as main structure-building component the long chain fibrous
cellulose portion which is present in naturally occurring
cellulose-containing cells, in particular those of lignified
plants. In particular embodiments, the fibres are isolated from
lignified plants by digestion steps removing or reducing the
content of lignin and other extractables and optional bleaching
steps. The cellulosic fibres can also stem from non-wood sources
such as annual plants.
The cellulosic fibres to be used may be of regenerated type (e.g.
Lyocell), although the use of other types of pulps may be
preferred. The pulps employed can be a primary fibrous material
("virgin fibers") or a secondary fibrous material (recycled pulps).
The pulp can stem from lignin-free or low lignin sources, such as
cotton linters, esparto (alfa) grass, bagasse (e.g. cereal straw,
rice straw, bamboo, or hemp), kemp fibres, Miscanthus grass fibers,
or flax (also referred to as "non-wood fibers" in the description
and the claims). In particular embodiments, the pulp is produced
from ligno-cellulosic material, such as softwood (which typically
originates from conifers) or hardwood (typically from deciduous
trees).
It is possible to use "chemical pulps" or "mechanical pulps",
whereby the use of chemical pulps may be preferred.
As used herein, "chemical pulps" are, according to DIN 6730,
fibrous materials obtained from plant raw materials of which most
non-cellulosic components have been removed by chemical pulping
without substantial mechanical post treatment. As used herein,
"mechanical pulp" is the general term for fibrous material made of
wood entirely or almost entirely by mechanical means, optionally at
increased temperatures. Mechanical pulp can be sub-divided into the
purely mechanical pulps (groundwood pulp and refined mechanical
pulp) as well as mechanical pulps subjected to chemical
pre-treatment, such as chemo-mechanical pulp (CMP), or chemo-thermo
mechanical pulp (CTMP).
Typical properties of tissue paper include the ready ability to
absorb tensile stress energy, their drapability, good textile-like
flexibility, properties which are frequently referred to as bulk
softness, a high surface softness, a high specific volume with a
perceptible thickness, as high a liquid absorbency as possible and,
depending on the application, a suitable wet and dry strength as
well as an interesting visual appearance of the outer product
surface. These properties allow tissue paper to be used, for
example, as cleaning cloths (e.g. household towels), sanitary
products (e.g. toilet paper, hand towels), paper handkerchiefs,
cosmetic wipes (facial tissues) or as serviettes/napkins.
In particular embodiments, aqueous adhesive composition used to
bond at least two fibrous plies such as tissue paper plies and/or
nonwoven plies together includes (i) an adhesive component and (ii)
a dermatologically acceptable acid, and optionally the
corresponding salt thereof. In one embodiment, the remainder is
water. The "aqueous adhesive composition" can also be referred to
and described as "water-based adhesive" including a
dermatologically acceptable acid, and optionally the corresponding
salt thereof.
As used herein, the term "adhesive component" is to be understood
as the one or more chemical substance(s) that correspond to the
non-aqueous component/s of water-based adhesives suitable for
bonding/laminating fibrous webs of tissue paper and/or nonwoven.
This adhesive component can include an adhesive polymer as main
component (more than 50 wt. %, e.g. more than 80 wt. %, based on
the total weight of the adhesive component) or as sole component.
Besides the adhesive polymer, the adhesive component may include
common auxiliary substances used in water-based adhesives such as
tackifiers, viscosity-adjusting substances or dispersion aids.
The aqueous adhesive composition may also contain a colorant which
can be used to make the applied pattern of adhesive composition
visible.
In particular embodiments, the solid content of the adhesive
component in the aqueous adhesive composition is 2 to 50 wt.-%, 2.5
to 20 wt.-%, or e.g. 3 to 10 wt.-%.
The adhesive polymer can be a natural polymer or a synthetic
polymer and is soluble or dispersible in the final aqueous adhesive
composition. The natural polymer can be made from sources such as
(i) proteins and protein-based compounds such as casein, soya
proteins, zein, and gelatin, (ii) gums and gum-like materials such
as gum arabic, gum tragacanth, gum ghatti, Indian gum, mucilage and
the like, (iii) polysaccharide-based materials such as starch and
processed starch, dextrins, agar, pectin, and the like or (iv)
glues derived from animal products such as hides, bones, and fish
offal. The synthetic polymers can be selected from PEI
(polyethyleneimine), PAE (polyamidoamin-epichlorhydrine) and PVAm
(polyvinylamine), polyvinyl alcohol (PVA), polyvinyl acetate
(PVAC), vinyl acetate-ethylene (VAE), polyvinylpyrrolidone (PVP),
sodium polyacrylate, polyethylacrylate, polymethacrylic acid,
polyurethanes and styrene-butadiene, and water-soluble or
-dispersible cellulose-based compounds such as carboxymethyl
cellulose, sodium carboxymethyl cellulose, methyl cellulose, and
ethyl cellulose, or any combination thereof. In particular
embodiments, the synthetic polymer is a polyvinyl alcohol polymer
or water-soluble or water-dispersible cellulose-based compound. The
natural polymer or synthetic polymer can be of any water-soluble or
water-dispersable molecular weight sufficient to form an adhesive.
In general, the adhesive polymer, i.e. the natural polymer or
synthetic polymer, may have a weight average molecular weight of
from about 40,000 to about 120,000, or from 70,000 to 90,000 (as
determined by GPC).
The dermatologically acceptable acid (which may also be referred to
as "skin-compatible") can be water-soluble. In embodiments, the
solubility in water (at 25.degree. C.) is at least 1 g/L, in
particular and with increasing preference at least 10 g/L, at least
50 g/L, at least 100 g/L.
In embodiments, the acid is selected from (i) inorganic acids such
as boric acid, (ii) organic, optionally hydroxylated, acids having
2 to 24 carbon atoms, and (iii) polymeric organic acids such as
polyacrylic acid. Optionally, each of these acids is combined with
a salt thereof, in particular a metal salt thereof to form a
buffer.
In embodiments, the salt-forming metal is selected from alkali and
alkaline earth metals including, but not limited to, sodium,
potassium, calcium, and other. Thus, in one example, when the
chosen acid is lactic acid, suitable metal salts thereof would
include sodium lactate and potassium lactate.
In embodiments, the organic, optionally hydroxylated, acid
according to item (ii) has 2 to 18, 3 to 10, or in particular 3 to
6 carbon atoms, and can be saturated or unsaturated. The organic,
optionally hydroxylated, acid according to item (ii) can be a mono-
or poly (e.g. di-) carboxylated acid. In particular embodiments,
the organic, optionally hydroxylated, acid according to item (ii)
is selected from citric acid, lactic acid, isoascorbic acid,
glycolic acid, malic acid, tartaric acid, glycolide (a cyclic dimer
of a glycolic acid which hydrolyzes to form two glycolic acid
molecules), acetic acid, dehydroacetic acid, oleic acid, palmitic
acid, stearic acid, behenic acid, palm kernal acid, tallow acid,
salicylic acid, ascorbic acid, sorbic acid, benzoic acid, succinic
acid, or any combinations thereof.
In particular embodiments, the acids are saturated and hydroxylated
and include citric acid, lactic acid, isoascorbic acid or any
combinations thereof. In yet more particular embodiments, the acid
is lactic acid together with a corresponding metal salt, such as
sodium lactate or potassium lactate.
As mentioned before, acids and salts of the corresponding acids
could be added together (e.g. lactic acid and sodium lactate) to
provide a "buffering" effect, which helps to keep the desired pH
stable. Accordingly, it can be preferred to make use of an aqueous
adhesive composition including both a dermatologically acceptable
acid and a salt thereof while both are present in amounts providing
a pH buffering capacity.
In one embodiment of the multi-ply fibrous product, said acid and
optionally the salt thereof are provided in such an amount that the
pH of the multi-ply fibrous product, such as the tissue paper,
nonwoven or hybrid product measured according to ISO 6588-1:2012(E)
is in the range of from 4.3 to 6.4, 4.5 to 6.2, or e.g. 4.8 to
6.
In one embodiment, the aqueous adhesive composition contains the
acid and optionally the salt thereof in a molar amount of 0.1 to 10
mol/1, 0.5 to 5 mol/l, or e.g. 1 to 3 mol/1.
In embodiments, the pH (measured at 25.degree. C.) of the aqueous
adhesive composition is 1 to 6, 1.5 to 4, or 2 to 3.
In one further embodiment, the aqueous adhesive composition has
been applied to the multi-ply fibrous product, in particular a
nonwoven or tissue paper product or a hybrid thereof, such as a
tissue paper product, and is present therein in an amount (based on
the total weight of all ingredients except water) of 0.01 to 2
wt.-%, or 0.1 to 1.3 wt.-%, with respect to the weight of the
multi-ply fibrous product. These values can be calculated by
dividing the amount of aqueous adhesive composition (total weight
of all ingredients except water) applied to the tissue paper
product, expressed as g/m.sup.2, through the basis weight of the
dry tissue paper product which is also expressed as g/m.sup.2. As
used herein, "dry" tissue paper means conditioned as specified
below in the experimental section.
The aqueous adhesive composition may have a viscosity of 1 to 500
mPas, or 1 to 200 mPas measured at 25.degree. C. using the
viscosimeter Brookfield LV-DV-I from Brookfield Engineering
Laboratories, Inc. using the spindles and rotational speeds given
in the experimental section. Alternatively, the viscosity may be
adjusted to the range of 25 to 150 mPas, or 70 to 125 mPas.
Since the addition of a dermatologically acceptable acid, e.g.
lactic acid to the adhesive composition can have an influence on
the viscosity thereof, and thereby on the handling and application
properties of the adhesive composition, it can be preferred to use
an amount of acid leading to viscosities within these ranges.
According to the further embodiments, the plies of the multi-ply
fibrous product include, as paper-making fibers, (i) only
non-recycled cellulosic fibers, (ii) only recycled cellulosic
fibers, or (iii) a mixture of non-recycled cellulosic fibers and
recycled cellulosic fibers in a weight ratio of 99/1 to 1/99, e.g.
90/10 to 10/90 or 80/20 to 20/80, wherein in any of (i), (ii) or
(iii) the cellulosic fibers can be selected from wood fibers such
as softwood or hardwood fibers and non-wood fibers such as fibers
from annual plants, and combinations thereof. Since fibrous
products made from recycled cellulosic fibers tend to have higher
pH values, greater amounts of acid may be required to prevent a
negative impact on natural skin pH.
Depending on the type of multi-ply fibrous product, the number of
fibrous plies such as tissue paper plies and/or nonwoven can be 2
to 8, in particular 2 to 6, e.g. 2 to 5. In very thick products
having higher ply numbers, the adhesive composition is usually not
added to one of the outer plies to bond all plies together but to
the 2nd or 3rd ply (if there are 2 or 3 inner plies located between
the two outer plies). The adhesive will then migrate from the ply
to which it has been applied to the other plies, either
automatically if the plies are superimposed and brought into
contact with each other, or at the latest if pressure is applied
(typically in a roll nip) to those areas carrying the adhesive
composition. In this manner, all plies can be bonded together.
The aqueous adhesive composition can be applied to the entire
surface, or a part thereof, in so-called "application zones".
Within these application zones the adhesive composition may be
applied as a continuous coating or in the form of one or more
regular or irregular patterns. Regular patterns can for instance be
generated by combined adhesive/mechanical (e.g. by embossing)
ply-bonding techniques explained below. The application zone, or
the sum of all application zones, may constitute at least 50%, or
at least 80% of the surface area of the multi-ply fibrous product.
In particular embodiments, the application zone includes the
central area of the multi-ply fibrous product which most likely
comes into contact with the skin of the user.
The pattern/s may include/s discrete and/or partially overlapping
elements such as dots, circles, lines, stripes, curves, polygons,
etc. which may form design elements such as flowers, leaves,
etc.
In particular embodiments, the adhesive composition is applied in a
pattern, such as in a pattern that coincides partially or fully
with a pattern of protuberances resulting from embossing at least
one ply. In one embodiment of the multi-ply fibrous product (e.g.
toilet paper), at least one outer ply this embossment pattern on
substantially at least 50%, or at least 80% of its surface, which
may include the central area of the multi-ply fibrous product.
In one embodiment, the multi-ply fibrous product shows an
essentially even coverage by the aqueous adhesive composition over
its surface. As used herein, "coverage" means the distribution of
an aqueous adhesive composition by means of at least one regular or
irregular pattern (i.e. one or two regular patterns) between at
least two plies of the multi-ply product. This "coverage" can
include the central area of the multi-ply fibrous product.
The adhesive composition can be applied by techniques usual in the
art such as spraying, roll application, printing, using a
non-contact application system as developed, e.g. by WEKO (Weitmann
& Konrad GmbH & Co. KG), or slot die application.
After the application of the aqueous adhesive composition, no
specific drying step is required. Typically, the fibrous plies,
such as tissue paper plies and/or nonwoven, will adsorb the free
water content of the aqueous adhesive composition. In addition,
some water may also evaporate when the multi-ply fibrous product is
left standing at the air.
In embodiments, at least two, or, in particular embodiments, all
fibrous plies such as tissue paper plies and/or nonwoven plies are
combined together by using an aqueous adhesive composition
including an acid or a buffer system, or by combining adhesive ply
bonding with mechanical ply bonding (e.g. by knurling or
embossing). During adhesive bonding, a film of adhesive is
deposited over the entire surface area, or a part thereof, of at
least one of the plies, then the adhesive-treated surface is placed
in contact with the surface of at least one other ply, as explained
below in further detail. Two plies are bonded together by applying
the adhesive composition to the inner side of one of the two plies.
When more than two plies are to be bonded together it is frequently
also sufficient to apply the adhesive composition only to one of
these plies, e.g. onto the inner side of one of the two outer
plies, because the adhesive composition will migrate to the other
plies as well and bond all plies together, especially if adhesive
ply bonding is combined with mechanical ply bonding and the
application of pressure to those areas carrying the adhesive
composition. During the mechanical combination, the plies may be
combined by knurling, or by compression, or by embossing. Embossing
is a process by which a raised or depressed design is produced,
generally by pressure between engraved rolls or plates or between
an engraved roll or plate and an elastic or a deformable supporting
surface. This can result for example in a dry crepe tissue ply
having a particular relief or indentation. The thickness of the dry
crepe tissue ply or of the multiple plies is increased after
embossing compared with its initial thickness.
In one embodiment, the multi-ply fibrous product, such as tissue
paper product, nonwoven product or hybrid thereof, has two outer
plies, and optionally further plies located therebetween, wherein
at least one outer ply is embossed, thereby forming protuberances
and wherein the aqueous adhesive composition is applied to the
distal end of at least a part of the protuberances which are
arranged such as to bond together the two outer plies, and
optionally further plies located therebetween. In this embodiment,
the lower outer ply may also be "flat", i.e. free of protuberances
resulting e.g. from embossing, while the aqueous adhesive
composition is only applied to the distal ends of protuberances of
the upper outer ply in order to join the outer plies (and e.g. an
optionally present center ply) together.
Some techniques for embossing fibrous plies, in particular nonwoven
plies including cellulosic fibers or tissue paper plies in
combination with the application of the aqueous adhesive
composition are explained below.
For manufacturing multi-ply fibrous products, especially tissue
products, especially bathroom tissue and household tissue, known
manufacturing methods for embossing and adhesively bonding of the
plies can be used such as the Goffra Incolla/spot embossing, DESL
(Double Embossing Single Lamination), and Pin-to-Pin/Foot-to-Foot.
Before ply bonding, the plies are often embossed in nips of an
embossing roll and an anvil roll.
In the first mentioned manufacturing method, Goffra Incolla, a
first web is directed through the nip between an embossing roll and
an anvil roll. In this nip, the web is provided with an embossing
pattern. Thereafter, an application roll applies adhesive to those
parts of the first web at which there are protruding embossing
elements in the embossing roll. The adhesive is transported from an
adhesive bath via an adhesive transfer roll to the application
roll. A second web is transported to the first web and adhesively
bonded to the first web in the nip between the so-called marrying
roll and the embossing roll. The adhesive bonding takes place at
those portions at which the adhesive was applied.
The second manufacturing method (DESL) is very similar to the
above-described Goffra Incolla method. It includes an additional
pair of rolls including a second embossing roll and a second anvil
roll. The additional pair of rolls serves to emboss the second web
before it is adhesively bonded to the first web using the marrying
roll. Typically, the additional pair of rolls is placed close to
the first pair of rolls and the marrying roll. In one special case
of the general DESL-manufacturing method, the embossing elements of
the first embossing roll and the embossing elements of the second
embossing roll are arranged such that the embossed elements of the
first embossed ply and the embossed elements of the second embossed
ply fit into each other similar to a gearing system. This serves to
achieve a mutual stabilization of the two plies. However, for the
DESL manufacturing method such correlation between the embossed
elements of the first, upper ply and the second, lower ply, is not
required.
The third manufacturing method (Pin-to-Pin/Foot-to-Foot) is similar
to the DESL method. By means of two pairs of rolls both the upper
ply and the lower ply are embossed, respectively. Adhesive is
applied onto the embossed protrusions ("protuberances") of the
first ply. The ply bonding, however, is not achieved by means of a
marrying roll as in the DESL method but is achieved directly by
means of the protruding embossing elements of the second embossing
roll. In order to achieve this, an exact adjustment of the width of
the gap between the first embossing roll and the second embossing
roll is required, which is mainly defined by the individual
thickness of both webs (upper ply and lower ply). Further, the
embossing rolls have to be designed such that at least some of the
protruding embossing elements of both rolls face each other. This
is the reason why the terminology Pin-to-Pin or Foot-to-Foot
embossing is used.
Further knurling can be used.
One suitable lamination technique has been described in WO
2011/035803 and leads to a 3 ply fibrous product including a middle
ply nesting with its protuberances into the pillow-like chambers of
the first ply and a bottom ply which can be free of
protuberances.
One particular lamination technique is shown in the appended
Figures and explained in the examples and is related to the
teaching of US 2003/0129363 assigned to Georgia Pacific France.
This embodiment, also illustrated by FIGS. 1 to 4, concerns a
fibrous multi-ply product, such as tissue paper product, nonwoven
product or hybrid thereof, including three plies, i.e. an embossed
upper outer ply (3), and an embossed lower outer ply (1), each
outer ply (1,3) including patterns in relief including at least in
part discrete protuberances, and a central ply (2), the distal
areas of at least part of the protuberances of each outer ply (1,3)
facing the central ply, and at least one of the upper outer ply (3)
and lower outer ply (1) having a pattern density of at least 10, or
at least 20 protuberances/cm.sup.2, the lower outer ply (1)
including a first pattern (15a, 15b) and a second pattern (16), the
height (13) of the first pattern being less than the height (14) of
the second pattern, wherein the central ply (2) and the upper outer
ply (3) are joined in a nested mode, and by means of the applied
adhesive composition (12), to said lower outer ply (1) at a level
of at least part of the tips of the second pattern of said lower
outer ply, wherein the height of the protuberances of the second
pattern can be 50% to 200% greater than the height of the
protuberances of the first pattern.
In an embodiment, applying the aqueous adhesive composition is in a
manner that the "gluing surface" (or "bonded surface") is in a
range of 1 to 20%, 2 to 10%, or 4 to 8%. As used herein, "gluing
surface" means the proportion of the total surface of the outer
plies of the multi-ply fibrous product including at least two
fibrous plies, for example a multi-ply nonwoven product, a tissue
paper product or a hybrid thereof, that is bonded to each other or,
if applicable, to one or more inner plies, by means of the aqueous
adhesive composition. If there are two gluing units or more
applying a blend acid/glue to one or more fibrous plies e.g. tissue
paper plies and/or nonwoven plies, in different not-overlapping
patterns, the respective gluing surfaces are added. Referring e.g.
to FIG. 2, the "gluing surface" can be determined (e.g. visually,
or with the aid of a microscope) by adding the individual
adhesively bonded areas (12), which correspond to the macro
embossed areas (16) shown in FIGS. 3A and 3B, and dividing the sum
thereof through the total surface area (plan view) of the tissue
paper product. Referring e.g. to the design shown in FIGS. 3A and
3B, the "gluing surface" in % can also be calculated by dividing
the total area of the macro embossing (16), as plan 2-dimensional
view, through the total surface of the fibrous product.
Various techniques exist in the art to adjust the amount of aqueous
adhesive composition applied on the multi-ply fibrous product. If,
as explained above, the aqueous adhesive composition is applied to
the distal ends of at least a part of the protuberances (resulting
from embossing), the aqueous adhesive composition can be supplied
to the embossing unit by an arrangement of rolls shown in FIG. 1.
This arrangement involves roll (6) with an engraved surface, e.g.
an anilox roll and applicator roll (7), e.g. a rubber roll with an
even surface. In this case, the amount of aqueous adhesive
composition can be adjusted by (i) changing the surface volume of
the engraved cells of roll (6) to values ranging from 9 to 30
cm.sup.3/m.sup.2 (for example volumes: 18 to 21 cm.sup.3/m.sup.2)
and/or (ii) adjusting the speed of engraved roll (6) to values of 3
to 40% of the line speed (for example speed: 7 to 15%, e.g.
10%).
The multi-ply fibrous product, such as tissue paper product,
nonwoven product or hybrid thereof, such as tissue paper product,
can be selected from a wipe, a sanitary product such as toilet
paper, a paper handkerchief, a household towel, a towel, a tissue
for facial use, a napkin/serviette, bed linen or a garment. In
particular embodiments, the multi-ply fibrous product is a toilet
paper having 2 to 8 plies, or 2 to 6 plies.
In an aspect, provided is a process for the manufacture of a
multi-ply fibrous product, such as a tissue paper product, nonwoven
product or hybrid thereof, including: a) providing at least two
fibrous webs, such as tissue paper and/or nonwoven webs, for
example at least two tissue paper webs, b) optionally embossing at
least one web in order to provide at least one pattern of
protuberances, c) applying an aqueous adhesive composition
including an adhesive component and a water-soluble,
dermatologically acceptable acid, and optionally the corresponding
salt thereof, to at least one side of at least one fibrous web,
wherein, if at least one web is embossed, the aqueous adhesive
composition can be applied to the distal ends of at least a part of
the protuberances, d) superimposing the at least two webs in a
manner that the aqueous adhesive composition is located between at
least two superimposed webs, e) bonding the at least two webs
together, and f) optionally further steps for converting the bonded
webs to the final multi-ply fibrous product.
As to steps a) to e) reference can be made to the previous
description of the multi-ply fibrous product, such as a tissue
paper product, nonwoven product or hybrid thereof, and its
manufacture.
The combination of several plies (at least two) can be used to
confer to the final multi-ply fibrous product particular properties
such as thickness, bulkiness, softness, and strength.
When processing the bonded fibrous webs, e.g. tissue paper webs
and/or nonwoven webs including cellulosic fibers, to the final
product (optional converting step f), the following steps can be
used individually or in combination: cutting to size
(longitudinally and/or cross cutting) folding, imprinting,
perforating, application of lotions, smoothing, stacking, rolling
up and packaging.
EXAMPLES
The following test methods were used to evaluate the tissue papers
produced. The test samples were conditioned for at least 12 hours
at 50% relative humidity and 23.degree. C. prior to testing. As
used herein, reference to the weight of the raw tissue paper or the
tissue paper product, the weight has can be determined after
conditioning in the above-explained manner.
4.1. Basis Weight
The basis weight was determined according to EN ISO 12625-6:2005,
Tissue Paper and Tissue Products, Part 6: Determination of
grammage.
4.2. Caliper
The measurement is made by a precision micrometer (precision 0.001
mm) according to a modified method based on EN ISO 12625-3:2014,
Part 3. For this purpose, the distance created by a sample between
a fixed reference plate and a parallel pressure foot is measured.
The diameter of the pressure foot is 35.7+0.1 mm (10.0 cm.sup.2
nominal area). The pressure applied is 2.0 kPa+0.1 kPa. The
pressure foot is movable at a speed rate of 2.0+0.2 mm/s.
A usable apparatus is a thickness meter type L & W SE050
(available from Lorentzen & Wettre, Europe).
The base tissue (web) to be measured is cut into pieces of
20.times.25 cm and conditioned in an atmosphere of 23.degree. C.,
50% RH (Relative Humidity) for at least 12 hours. For the
measurement, a stack of 10 base tissue paper sheets is prepared and
placed beneath the pressure plate, which is then lowered. The
thickness value for the stack is then read off 5 seconds after the
pressure has been stabilized. The thickness measurement is then
repeated nine times with further samples treated and prepared in
the same manner.
The mean value of the 10 values is taken as thickness of 10 base
tissue sheets measured (in the following referred to as "10-ply
caliper").
The finished product to be measured (i.e. a one-ply or multi-ply
tissue paper product) is cut into pieces of 20.times.25 cm and
conditioned in an atmosphere of 23.degree. C., 50% RH for at least
12 hours.
For the measurement, one sheet is placed beneath the pressure plate
which is then lowered. The thickness value for the sheet is then
read off 5 seconds after the pressure has been stabilized. The
thickness measurement is then repeated nine times with further
samples treated in the same manner.
The mean value of the 10 values obtained is taken as thickness of
one sheet ("one-sheet caliper") of the finished product (e.g. a
two-ply hand towel) measured.
4.3. Viscosity
The viscosity of the composition was measured at 25.degree. C.
using the viscosimeter Brookfield LV-DV-I from Brookfield
Engineering Laboratories, Inc. Depending from the expected range of
viscosities, the following spindles (sp) and rotational speeds (v)
are used:
TABLE-US-00001 sp 1/v 100 rpm for x < 0.1 Pa s sp 2/v 100 rpm
for 0.1 Pa s < x < 1 Pa s sp 3/v 100 rpm for 1 Pa s < x
< 6 Pa s sp 4/v 100 rpm for x > 6 Pa s.
4.4 pH Measurement (Raw Tissue Paper/Tissue Paper Product)
As used herein, the following test method can be used to measure
the pH of the tissue paper products.
ISO 6588-1:2012(E)--cold extraction methodology
This method is based on the extraction of a representative sample
of the respective tissue paper product (2 g) with water of high
purity (100 mL) at a temperature between 20 and 25.degree. C. for 1
h. The extract was prepared, filtered and was treated in accordance
with this international standard. The pH of the extract was
measured at a temperature between 20 C and 25 C. The method yields
the average pH of the entire tissue paper product.
4.5 pH Measurement on Skin
Flat Electrode Methodology
Skin surface pH studies were conducted to study the effects of the
low pH tissue products on skin pH. Measurements were made on the
volar forearm before and after application of the test product.
Skin surface pH was measured using a flat-surface electrode,
calibrated in standard buffer solution at pH 4.0 and pH 7.0. The
electrode was dipped in 0.9 wt % NaCl in deionized water before
each measurement. 200 .mu.L of 0.9 wt % NaCl was added to the skin
and wiped using the tissue paper of embodiments of the invention.
Using a five-person panel, the tissue paper products of embodiments
of the invention were tested for their effect on the skin surface
pH of the forearm.
Example 1
Preparation of Aqueous Adhesive Composition
About 1 l of a potassium lactate buffer with a pH of 2 was prepared
by dissolving 85% lactic acid (264 g, 15% water) and KOH (5 g) in
H.sub.2O (736 g). The molar content ("molarity of acid") of lactic
acid calculated from these values was 2.366 mol/l. The molarity of
the acid refers to the total amount of added acid irrespective of
whether a part thereof is present as lactate due to the addition of
KOH.
Then, the buffer solution was mixed with 429 g of an aqueous
polyvinylalcohol-based adhesive (Swift.RTM.tak 1004, solid content
of ca. 18.0%; available from H.B. Fuller, Europe, pH ca. 4.5), and
resulting in a ratio of 70 wt.-% potassium lactate buffer solution
to 30 wt.-% Swift.RTM.tak 1004. After mixing the solid content of
the adhesive component was ca. 5.4 wt-% based on the entire aqueous
adhesive composition. The resulting aqueous adhesive composition
had a pH of ca.2.3.
Manufacture of Tissue Paper Product
Raw tissue paper webs produced in a conventional dry crepe process,
non-embossed having a caliper of 0.37 mm/sheet and a basis weight
of 56.8 g/m2 were prepared from a pulp mixture.
The roll paper was composed of three plies using only papermaking
fibers of non-recycled (virgin) type (100% of virgin fiber). The
ply composition was as follows: two outer plies made from 9%
softwood Kraft fibers, 88% eukalyptus Kraft fibers and 3% other
hard wood Kraft fibers; one inner ply made from 73% softwood Kraft
fibers, 20% hardwood Kraft fibers and 7% CTMP.
The raw tissue paper webs had a pH, as measured by ISO
6588-1:2012(E) of 7.7.
Ply-Bonding Step
Three of the manufactured tissue paper webs were supplied to the
embossing and gluing station illustrated in FIG. 1.
The first web (1) and the third web (3) were each advanced to the
rubber rolls (8a and 8b) and embossed by the engraved rolls (9a and
9b). The second web (2) forming later the middle ply in the
three-ply product was first advanced to the gluing unit (4) where
the aforementioned aqueous adhesive composition was applied to one
side of the web by the (level 2) protrusions (14) of the engraved
roll (9a) which presses the web against glue applicator roll (7).
The glue (aqueous adhesive composition) was applied only on the
level 2 engraving (14) having about the double height of the level
1 engraving (13).
The gluing unit (4) includes the glue chamber (5), which contained
the aqueous adhesive composition, an engraved anilox roll (6),
which transferred the aqueous adhesive composition (at room
temperature) from the glue chamber to the applicator roll (7), a
rubber roll with even surface, which transferred the adhesive
composition to the second web (2). A doctor blade (not shown in
FIG. 1) metered the amount of glue on the anilox roll which is
running at a differential speed to lower the amount of glue
transferred to the applicator roll. The applicator roll is running
at line speed. The anilox roll possesses at its surface small cells
delivering a specific glue volume per m.sup.2.
According to an embodiment, the volume of the anilox roll was
adjusted to be 18 to 21 cm.sup.3/m.sup.2, the speed of the anilox
roll was adjusted to be 10% of the line speed and the glue-bonded
area, which corresponds to the total area of all bonded areas (12)
as shown in FIG. 2, was 4 to 6% of the total surface of the tissue
paper product.
The three paper tissue webs were superimposed, first web (1) and
(2), then also web (3) in the nip between roll (9a) and (9b), where
however no pressure was applied, and further advanced to the nip
between engraved roll (9a) and marrying roll (10) where all three
webs were bonded together by pressing the glue covered areas (12)
together.
The bonded webs were then cut-to-size, perforated and further
converted to toilet paper rolls.
As it can be seen from FIGS. 2 and 3, the resulting three-ply
toilet paper displays three embossing patterns: the micro-embossing
patterns (15a, 15b) (cf. level 1 engraving, 13) and the
macro-embossing pattern (16) (cf. level 2 engraving, 14) which also
serves as decorative pattern.
All embossing patterns of the prepared tissue paper product covered
the entire surface of the tissue paper product.
The applied amount of said adhesive composition, in terms of all
ingredients except water, was 0.39 wt.-%, based on the basis weight
of the tissue paper product.
The pH value of the tissue paper product was 5.6 as determined by
the ISO 6588-1:2012(E) method.
Comparative Example 1 and Examples 2 to 12
12 different three-ply tissue paper products (toilet paper) were
produced in the same manner as set forth in Example 1 apart from
the differences shown in table 1 and explained below:
In comparative example 1 and in examples 2 to 5 as well as examples
8 to 12 the same paper-making fibers and ply composition were used
as in example 1.
In examples 6 and 7, the roll paper was composed of 3 plies
comprising 26% recycled fibers and 74% virgin fibers. The ply
composition was as follows: two outer plies made from 60% bleached
Eucalyptus Kraft Pulp and 40% bleached Softwood Kraft pulp one
inner ply made from 20% bleached Eucalyptus Kraft Pulp and 80%
deinked pulp fibers
In Comparative Example 1 (CEx 1), no acid was added to the aqueous
adhesive composition.
In examples 6 and 7, raw tissue paper webs were prepared according
to the conventional dry crepe process from a pulp mixture
comprising 26% recycled fiber and 74% virgin fibers.
Zelura Glue used in example 12 is a methyl cellulose-based adhesive
and commercially available as a solid from Henkel. 33.3 parts by
wt. solid were dissolved in 966.7 parts by wt. water to produce
about 11 of aqueous adhesive.
As seen from these results, all examples led to an effective change
in pH. The adhesive power of the prepared aqueous composition was
good despite the presence of greater amounts of acid/buffer.
TABLE-US-00002 TABLE 1 Example CEx 1 2 3 4 5 6 7 Raw tissue paper
pH (ISO 6588-1) 7.7 7.7 7.7 7.7 7.7 9.0 9.0 Paper-making fibers
Virgin virgin virgin virgin virgin recycled + recycled + virgin
virgin Raw tissue paper [g/m.sup.2] 56.8 56.8 56.8 56.8 56.8 49.3
49.3 basis wt. Gluing Surface % 4.4 4.4 4.4 4.4 4.0 4.0 8 Anilox
speed % 10 10 10 10 10 10 10 Adhesive type/ Swift .RTM.tak 1004 [g]
180 180 180 180 180 180 180 solid content Zelura Glue [g] -- -- --
-- -- -- -- Water content H.sub.2O [g] 820 820 820 820 820 820 820
Buffer Lactic Acid [g] -- 616 352 410.6 616 616 616 Citric Acid [g]
-- -- -- -- -- -- -- KOH [g] -- 23.2 10 11.6 23.2 23.2 23.2
H.sub.2O [g] 2000 1717.3 1648 1922.6 1717.3 1717.3 1717.3 Molarity
acid [M] -- 2.366 1.604 1.604 2.366 2.366 2.366 pH -- 2 2 2 2 2 2
pH of adh. comp. 4.51 2.27 2.22 2.20 2.27 2.27 2.27 Viscosity adh.
Comp. (mPa s) 63 117 93 85 117 117 117 Ratio (by wt.)
Adhesive/Buffer 100:0 30:70 33:67 30:70 30:70 30:70 30:70 Tissue
paper product pH (ISO 6588-1) 7.2 5.3 5.9 5.9 5.1 6.0 5.9 Example 8
9 10 11 12 Raw tissue paper pH (ISO 6588-1) 7.7 7.5 7.7 7.5 7.5
Paper-making fibers virgin virgin virgin virgin virgin Raw tissue
paper [g/m.sup.2] 56.8 56.2 56.8 56.2 56.2 basis wt. Gluing Surface
% 8 8 4.4 8 8 Anilox speed % 10 30 10 10 10 Adhesive type/ Swift
.RTM.tak 1004 [g] 180 180 180 180 -- solid content Zelura Glue [g]
-- -- -- -- 33.3 Water content H.sub.2O [g] 820 820 820 820 966.7
Buffer Lactic Acid [g] 616 616 678.8 -- 528 Citric Acid [g] -- --
-- 452.8 -- KOH [g] 23.2 23.2 25 40 20 H.sub.2O [g] 1717.3 1717.3
1892.6 1861.1 1472 Molarity acid [M] 2.366 2.366 2.366 1.010 2.366
pH 2 2 2 2 2 pH of adh. comp. 2.27 2.27 2.24 2.25 2.17 Viscosity
adh. Comp. (mPa s) 117 117 77 80 25 Ratio (by wt.) Adhesive/Buffer
30:70 30:70 28:72 30:70 33:67 Tissue paper product pH (ISO 6588-1)
5.0 4.3 5.8 5.0 6.0
Example 13
Using a five-person panel and the flat electrode method described
before, the tissue paper product of example 7 was tested for its
effect on the skin surface pH of the forearm. The results are
listed in Table 2 below.
TABLE-US-00003 TABLE 2 Test person #1 #2 #3 #4 #5 Initial pH 5.20
5.83 5.55 5.55 5.79 Skin treatment with/resulting pH Ex. 7 5.03
5.40 5.40 5.32 5.45
The above results show that the pH of healthy skin can be
stabilized by means of a tissue paper in accordance with
embodiments of the present invention, even if the raw tissue paper
used therein has a fairly high pH (pH 9.0 as in the case of example
7).
* * * * *